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　　The hollow section usually loses its bearing capacity at 450 ~ 650 ℃, which leads to great deformation, resulting in bending of steel column and steel beam. As a result, it can not continue to be used due to excessive deformation. Generally, the fire resistance limit of the unprotected hollow section is about 15 minutes. The length of this time is also related to the heat absorption rate of the component. The following describes the fire protection measures for several different hollow section.

　　1. Outsourcing layer.Hollow section can be cast-in-situ or sprayed by adding an outer coating on the surface of hollow section. The outer layer of cast-in-place solid concrete is usually reinforced with steel wire mesh or reinforcement to limit the shrinkage cracks and ensure the strength of the shell.

　　2. Water filling. Water filling in ASTM A36 Gr.B 32mm Square Hollow Section is the most effective protective measure against fire. This method can keep the temperature of hollow section low in the fire, water circulates in the hollow section and absorbs the heat of the material itself. After cooling, the heated water can be recycled, or cold water can be introduced into the pipeline to replace the heated water.

　　3. Shielding. The hollow section is set in the wall or ceiling composed of refractory materials, or the components are wrapped in the gap between two walls. The purpose of fire prevention can be achieved by adding a little refractory materials or not. This is the most economical way to prevent fire.

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